Back when I was younger and challenges were mostly mental, I did participate in a group hike to the bottom of the Grand Canyon (via the Hermit trail). Yes, the hike back up was tough, but we had two nights' camp out at the bottom, right by the river, in what for us Canadians was pleasant August type climate, while we had started in a bit of snow at the top (late October) and the rest day was beautiful.

During the hike and stay at the bottom we encountered about half a dozen other people. It really was grand.

In Yosemite, all you have to do is outhike the "Reebok hikers" as we called them back then. An hour's serious walk gives you relative solitude.

And in Zion, last time we were there, a couple of us did not do Angels Landing. Instead we went to another spot equally high up where it was peaceful and quiet, and took telephoto pictures of the others on Angels Landing (note: I've been up there and it's awesome, but in that terrain a crowd sounds scary).